1. Field of the Invention
The invention relates to the medical instrument engineering, and namely to the instruments for stopping heart fibrillation by applying short-time electric pulses, i.e. to defibrillators.
The invention may prove most advantageous in medicine for treatment during acute and chronic rhytm disturbances, particularly during resuscitation.
Due to the fact that defibrillation of the heart is accompanied by excessive painful sensations which can lead to the pain shock, it is necessary to apply a short-time narcosis during treatment. It is most expedient to use a short-time electronarcosis caused by interference currents, said electronarcosis being characterized by the absence of side and toxic effects on the patient's organism, which effects are especially dangerous in predeterminal and terminal states.
Instruments intended for heart defibrillation are known for a comparatively long time, however up to now prior art defibrillators cannot provide in the process of operation an automatically strict sequence of effects of a narcotizing and defibrillating current on a patient which fact, during emergency medical treatment of a patient being in a grave condition, may lead to operator's mistakes thus decreasing safety of the treatment procedure.
2. Description of the Prior Art
Known in the art are defibrillators (British Pat. No. 1,481,469, I. V. Venin et al., DI-03 and DKI-01 defibrillators, "Novosti meditsinskogo priborostroenia", VNIIMP, Moscow, 1973, pp. 48-53), comprising a discharging circuit provided with a storage capacitor, a controlled contactor, and electrodes, being connected in series therebetween. The storage capacitor is connected to a voltage source for charging said storage capacitor, and to the input of a unit for adjusting and controlling a voltage across the storage capacitor. The output of said unit for controlling the voltage is connected to the input of the voltage source. A unit for starting defibrillation is connected to the input of the controlled contactor.
The unit for adjusting and controlling the voltage is constructed as a kilovoltmeter and a pushbutton for switching on the voltage source.
Prior to starting the defibrillation procedure, electrodes of an electronarcosis apparatus are fixed on the patient's head, while electrodes of the defibrillator are fixed on the chest. Then an operator depresses the pushbutton of the unit for adjusting and controlling the voltage, and holding the pushbutton in the depressed position, carries out controlled charging the storage capacitor. Following this, the operator actuates the electronarcosis apparatus and without interrupting the effect of the narcotizing current on the patient, switches on the unit for starting defibrillation. In doing so, there occurs starting the controlled contactor, and a pulse of the defibrillator is fed to the patient's chest. Then the operator disconnects the electronarcosis apparatus.
With such a procedure, the time of effect of electronarcosis prior to and after the effect of the defibrillating current is determined by the operator. This can lead to operator's mistakes, especially under strenous conditions of emergency treatment of a patient being in a grave condition, which mistakes worsen the patient's state. For example, the duration of electronarcosis may be excessively decreased thus resulting in the fact that defibrillation will occur prior to the beginning of the narcotizing effect of the current. Moreover, due to a mistake, defibrillation may also take place after the narcotizing effect of the current is over.
Said disadvantages are to a certain degree eliminated by a defibrillator (I. V. Venin et al., Di-03 and DKI-01 defibrillators, "Novosti meditsinskogo priborostrojenija", VNIIMP, Moscow, 1973, pp. 48-53) comprising a discharging circuit provided with a storage capacitor, a controlled contactor, and electrodes, being connected in series therebetween. The storage capacitor is connected to a voltage source for charging said storage capacitor, and to the input of a unit for adjusting and controlling a voltage across the storage capacitor.
The output of said unit for adjusting and controlling the voltage is connected to the input of the voltage source. The defibrillator further comprises an AND gate having two inputs and an output, and a unit for starting defibrillation. The first input of the AND gate is connected to the output of the unit for starting defibrillation, while the second input of said AND gate is a synchronizing input of the defibrillator to synchronize the effects of the defibrillating current and of an external source of a signal, and the output of the AND gate is connected to the input of the controlled contactor.
Prior to starting the defibrillation procedure, an operator connects the synchronizing input of the defibrillator (the second input of the AND gate) to an electronarcosis apparatus following which electrodes of the electronarcosis apparatus are fixed on the patient's head, while electrodes of the defibrillator are fixed on the chest. Then the storage capacitor is charged up to a voltage necessary to carry out defibrillation, said voltage being automatically maintained at a predetermined level. The operator actuates the unit for starting defibrillation and then switches on the electronarcosis apparatus. As the patient is under the effect of the narcotizing current a signal is fed from the electronarcosis apparatus to the synchronizing input of the defibrillator (the second input of the AND gate). In doing so, at the output of the AND gate there appears a pulse which is fed to the contrlled contactor thereby actuating said contactor, and a pulse of the defibrillator is fed to the patient's chest against the background of the narcotizing effect.
However, in the process of operation of the above defibrillator, especially under conditions of treating patients being in the terminal state, there exists the danger of synchronous effect of electronarcosis and the defibrillating current on the patient when the operator switches on the unit for starting defibrillation while the voltage across the storage capacitor has not yet reached, in the process of charging said capacitor, the level required for defibrillation.
It is known that discharging the storage capacitor under a voltage being lower than that required for defibrillation, while coinciding with the vulnerable phase of the cardiac cycle, may cause heat fibrillation.
Said disadvantage is eliminated by the Defiscop defibrillator manufactured by the "Thomson" company (France), which defibrillator comprises a discharging circuit provided with a storage capacitor, a controlled contactor, and electrodes for defibrillation, being connected in series therebetween. The storage capacitor is connected to the output of a voltage source to charge said storage capacitor, and to the input of a unit for adjusting and controlling a voltage across the storage capacitor. The input of the voltage source is connected to the output of the unit for adjusting and controlling the voltage. The defibrillator further comprises a unit for starting the defibrillator, and two AND gate, each of said gates having two inputs and an output. The first input of the first AND gate is connected to the output of the unit for adjusting and controlling the voltage. The second input of the first AND gate is connected to the unit for starting defibrillation. The output of the first AND gate is connected to the first input of the second AND gate whose second input is a synchronizing input of the defibrillator. The output of said second AND gate is connected to the input of the controlled contactor.
Prior to starting the defibrillation procedure, the operator connects the synchronizing input of the defibrillator (the second input of the second AND gate) to an electronarcosis apparatus following which electrodes of the electronarcosis apparatus are fixed on the patient's head, while electrodes of the defibrillator are fixed on the chest. Then the storage capacitor is charged up to a voltage required for defibrillation. The magnitude of this voltage is then automatically maintained at a predetermined level. Following this, the operator actuates the unit for starting defibrillation and then switches on the electronarcosis apparatus. As the patient is under the effect of the narcotizing current, a signal is fed from the electronarcosis apparatus to the synchronizing input of the defibrillator (the second input of the second AND gate). A signal from the unit for starting defibrillation is fed to the first input of said second AND gate. It is understood that this signal may be fed only in the case when at the output of the unit for adjusting and controlling the voltage there exists a signal indicating that the level of the voltage across the storage capacitor required for defibrillation is reached. Thus, the effect on the patient of the defibrillating current being of a lower magnitude than required is eliminated in this defibrillator. After both signals have been fed to the inputs of the second AND gate, a pulse appears at the output thereof, said pulse being fed to the input of the controlled contactor. In doing so, said contactor gets actuated, and a pulse of the defibrillator is fed to the patient's chest against the background of the narcotizing effect.
However, in the process of operation of the above defibrillator, especially under conditions of treating patients being in the terminal state, there exists the danger of the effect of only the narcotizing current on the patient without subsequent defibrillation. This becomes possible due to the fact that using the above defibrillator, the operator accomplishes defibrillation being synchronous with electronarcosis by carrying out two subsequent actions: actuation of the unit for starting defibrillation and switching on the electronarcosis apparatus.
While the effect of the defibrillating current on the patient is possible only in the case when the defibrillator is completely ready for operation, the effect of the narcotizing current is also possible when the defibrillator is not ready for operation. Thus, the gravity of the situation when carrying out emergency treatment of the patient being in a critical state, may promote operator's mistakes, and utilization of the above described defibrillator may lead to unwarranted effects of the narcotizing current on the patient thereby decreasing safety of the treatment procedure.
Moreover, in operation of the above described defibrillator the operator has to spend some time for connecting the narcosis apparatus thereto, and to be especially careful to see which apparatus and in which sequence is to be put in operation. Under conditions of a strenous situation the above consideration results in a considerable complication of apparatus maintenance thereby leading to certain losses of time which time is so valuable during this period.